Backup method

ABSTRACT

The invention provides a method of backing up data, in which plural information processing units connected to a network are not required to monitor each other, and autonomously send data to the other information processing units to buck up the data. The method, using the plural information processing units connected to the network collects information as to a possibility of backing up the data from the other plural information processing units connected to the network, adds addresses for identifying the other information processing units to collected information, and stores the collected information in a storage device. When the backup becomes necessary, the method sends a backup request to the other information processing units selected on the basis of the information stored in the storage device, and sends backup data to the other information processing units that returned to accept the backup request.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese application JP2004-119868 filed on Apr. 15, 2004, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION

The present invention relates to a method of backing up data,specifically to a method of mutually backing up data by use of pluralinformation processing units connected to a network, a method ofrestoring backed-up data, and a system of the same.

It is a common practice to connect information processing units such ascomputers and storage devices to a network, and to process informationwhile exchanging data between these units. Some storage devices forrecording bulk data employ the RAID (Redundancy Arrays Of InexpensiveDisks) these days, and practically use the management technique thatintegrates the storage devices while using the SAN (Storage AreaNetwork) with the NAS (Network Attached Storage). These informationprocessing units such as computers and storage devices can write andread data, and they are often referred to as media. As long as it canwrite and read data, the media include an information processing unitthat is not necessarily connected to a network.

A general behavior prepares the so-called backup of retaining the copiesof currently used data in the other media, in order to prevent the datafrom disappearing, or to ensure the security of the data. When the mediais connected to a network, the backup of data in general automaticallystores the data in a different medium by a computer or a timer issuing aperiodic trigger. When the medium is not connected to a network, on theother hand, the operator manually issues a trigger for the backup toretain the data in a different medium.

In this method, the medium being the storage unit destined for thebackup data, or the backup time is settled in advance. Accordingly, inan accident or a disaster, since the medium destined for the backup orthe backup time is settled, there is a fear that this method cannot makethe backup of the data, and can lose the data.

As the technique to back up data in the media utilizing a network, theJapanese Published Unexamined Patent Application No. 2002-215474, forexample, proposes a technique to back up data on a network to whichplural servers are connected. This method creates a mirror of the datain more than two servers connected with the network, in which the pluralservers monitor the situations of themselves each other. As a result ofthe monitoring, when detecting an abnormality in one server, the methodmakes the servers cooperate to find out a server having sufficientstorage capacity, determines a substitutive server, and transfers thedata to the substitutive server to store the data. In this manner, theabove technique discloses a backup system, in which plural backupservers are always formed.

The Japanese Published Unexamined Patent Application No. 2003-223286proposes a storage system provided with an autonomously functionalstorage device, whereby a management server is made unnecessary. Thatis, in the storage system, a copy agent possesses the duplicate functionof a copying unit, a monitoring unit monitors the multiplicity of thecopying unit, and when the multiplicity is insufficient, the systemissues a duplicate request to other storage devices.

The technique disclosed in the Japanese Published Unexamined PatentApplication No. 2002-215474 searches for a substitutive server having amargin in the storage capacity, and sends the data to the substitutiveserver having the margin. However, this technique requires thesubstitutive server to monitor the multiplicity of the copying unit inthe other storage devices. The Japanese Published Unexamined PatentApplication No. 2002-215474 does not disclose a concrete method how tosearch for the substitutive server having the margin.

The technique disclosed in the Japanese Published Unexamined PatentApplication No. 2003-223286 saves the management server; however, thetechnique needs to autonomously monitor the other storage devices. TheJapanese Published Unexamined Patent Application No. 2003-223286 doesnot relate how to restore the data having been backed up.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a method of backing up data,in which plural information processing units connected to a network arenot required to monitor each other, and autonomously send data to theother information processing units to buck up the data.

The invention also provides a method of restoring backed-up data whichautonomously restores the data having been backed up in the otherinformation processing units in an original information processing unit.

According to one aspect of the invention, the method of backing up datauses plural information processing units connected to a network, whichincludes the steps of: collecting information as to a possibility ofbacking up the data from the other plural information processing unitsconnected to the network, adding addresses for identifying the otherinformation processing units to collected information, and storing thecollected information in a storage device, sending a backup request tothe other information processing units selected on the basis of theinformation stored in the storage device, when the backup becomesnecessary, and sending backup data to the other information processingunits that returned to accept the backup request.

As a preferable example, the method includes the steps of: sending afirst message for inquiry to a network from a first informationprocessing unit, returning a second message containing information as toa possibility of backing up the data to the first information processingunit from a second information processing unit that received the firstmessage, creating a first table on the basis of the second message bythe first information processing unit, which manages at leastinformation relating to the second information processing unit capableof backing up the data, and retaining the table in a storage device,sending backup data to the second information processing unit being arecipient of the backup data, selected from the first table, andcreating a second table for managing information including an address ofthe second information processing unit having been the recipient of thebackup data, and retaining the table in the storage device inside thefirst information processing unit.

The above second message includes a type of a medium that the secondinformation processing unit possesses, a free capacity of the medium,and information as to whether a backup request can be accepted, and thefirst table registers an address that specifies the second informationprocessing unit, the type of the medium, the free capacity of themedium, and the information as to whether a backup request can beaccepted.

The above second table preferably registers at least the address of thesecond information processing unit that sent the backup data, andinformation indicating success or failure of the backup.

And, the second information processing unit that received the backupdata from the first information processing unit preferably creates athird table that registers at least an address of the first informationprocessing unit having been a recipient of the backup data, and theinformation indicating success or failure of the backup, and retains thetable in the storage device.

And, before sending the backup data to the second information processingunit being the recipient of the backup data from the first informationprocessing unit, the method preferably includes the steps of: selectinga second information processing unit being a backup object withreference to the first table, and sending a backup request message tothe second information processing unit, and receiving a return messageas to whether the backup request can be accepted or not from the secondinformation processing unit.

In regard to restoring backed-up data, the first information processingunit requests, referring to the second table, to transfer the backupdata to the second information processing unit having been the recipientof the backup data, receives the backup data sent from the secondinformation processing unit, and stores the backup data in the storagedevice inside the first information processing unit.

The invention can be recognized as a program for executing the steps ofthe method of backing up data or the method of restoring data.

The invention can also be recognized as an information processing unitthat executes the backup processing and the restoration processing. Thatis, the information processing unit connected to a network, sends andreceives data to and from other plural information processing units,which includes: a CPU that executes data processing, a recording mediumthat stores data processed by the CPU, a nonvolatile memory that storesat least management information for bucking up data, and a communicationport connected the network and paths to connect the units. Thecommunication port sends a first message for acquiring state informationof the other information processing units to the network, and receives asecond message including information as to a possibility of backing upthe data, sent from the other information processing units. Thenonvolatile memory or the recording medium retains a first table,created on the basis of the second message, that manages informationrelating to the other information processing units being at leastcapable of bucking up the data. The CPU selects, in an abnormal state,the other information processing units being the recipients of thebackup data referring to the first table, issues a backup request to theother information processing units, executes processing for sending thedata stored in the recording medium to the other information processingunits that accepted the backup request, and creates a second table formanaging information including addresses of the other informationprocessing units having been the recipients of the backup data. Thenonvolatile memory or the recording medium retains the second table.

According to this invention, the plural information processing unitsconnected to the network are not required to monitor each other, and itis possible to autonomously transfer the backup data to the otherinformation processing units, and to archive the data. Also, it is easyto restore the data backed up in the other information processing units.

According to a preferable example, it is possible that the informationprocessing units mutually communicate the state information of theirs,including the free capacity for storing data through the network, andthat a certain information processing unit having an abnormalitydetected searches for other information processing units that aresuitable with reference to the state information to thereby transfer thebackup data to the other information processing units.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic configuration and an operational processof the automatic backup system in one embodiment of the presentinvention;

FIG. 2 illustrates the operational process of recovering backed-up datain the embodiment;

FIG. 3 illustrates the electronic mail protocol used in the backupsystem in the embodiment;

FIG. 4 illustrates a configuration of a media information managementtable 400 of the embodiment, which registers the other mediainformation;

FIG. 5 illustrates a configuration of a backup media management table500 of the embodiment, which manages the information of the mediacapable of backup;

FIG. 6 illustrates a configuration of a backup media management table500 of the embodiment, which manages the information of the mediacapable of backup;

FIG. 7 illustrates a configuration of a manifest table 700 of theembodiment, which manages the information of the recipient of the backuprequest;

FIG. 8 illustrates a configuration of a deposit table 800 of theembodiment, which manages the information of the originator of thebackup request;

FIG. 9 illustrates the electronic mail protocol used for recovering thebacked-up data in the embodiment;

FIG. 10 illustrates a configuration of a recovery management table 1000of the backup data in the embodiment; and

FIG. 11 illustrates a configuration of the media of the automatic backupsystem in the embodiment.

DESCRIPTION OF THE EMBODIMENTS

The embodiment will now be described with reference to the accompanyingdrawings.

FIG. 1 illustrates a schematic configuration and an operational processof the automatic backup system in one embodiment of the presentinvention.

Media 101 through 105, which can be represented by 101, are connectedeach other through a network 100. These plural media 101 each have theIP address inherent to them each, and sends/receives data each otherbetween the media. Here, the media signify the information processingunits such as computers and storage devices.

FIG. 11 illustrates a configuration of the media.

Each of the media possesses a CPU 1101 that executes informationprocessing, a memory 1102 that stores data and programs for theinformation processing, a timer 1103 having the timer function, anonvolatile memory 1104, a recording medium 1105, a communication port1106 that connects these media to the network 100; and these units areconnected with a bus or a LAN 1107. Here, the nonvolatile memory 1104archives various types of management tables, which are represented bythe table (the manifest table, described later) for managing themanagement information relating to the backup, for example, theinformation including the IP address and the data transfer capacity ofthe medium being the recipient of the backup request. The manifest willbe explained later. The recording medium 1105 is a storage device forstoring the backup data as well as the data and programs for the dataprocessing, which includes, for example, a RAID unit, a magnetic tapeunit, and an HDD and so forth.

The CPU 1101 possesses an abnormality detection function that detects anabnormality of the own medium 101 at each constant time intervals, and afunction that monitors a free data capacity in the recording medium1105. The information of the free data capacity obtained by themonitoring is retained in the memory 1102. Here, the abnormality of thedevice signifies the fault resulting from the hardware and software. Forexample, if there occurs a write/read error to a storage device, whichcannot be restored after specific frequency of retrials, the error isregarded as the abnormality of the device.

As the feature of this embodiment, each of the media 101 has the programin the memory 1102, which realizes the protocol for mutuallysending/receiving, through the network 100, the state information thatincludes the state of the device of the own media, free data capacity ofthe storage device, data transfer speed, and IP address. In the normalstate, each of the media 101 is carrying out a designated applicationwith the CPU 1101, and executes the processing according to thisprotocol when the backup becomes necessary.

In the processing according to this protocol, each of the media 101sends the request for acquiring the state information of the other mediaperiodically to the network 100. The other media 101 send the stateinformation of the media of its own to the other media according to thisprotocol. Carrying out the above process, each of the media 101 createsor updates the media information management table 400 (FIG. 4) describedlater, and retains it in the nonvolatile memory of its own, for example,in the manifest I/O device 1104.

When a specific one of the media 101 detects an abnormality of the owndevice, the media 101 broadcasts an Inquire message according to the UDPprotocol, for example, to the other media 102 to 105 through the network100 (FIG. 1A). The Inquire message 301 is composed of, as shown in FIG.3A, ‘Inquire’ as the message type, IP address of the own medium, and MCAaddress of the own medium.

Next, as shown in FIG. 1B, the other media 102 to 105 having receivedthe Inquire message 301 create an Inform message 302, and broadcast itto the network 100 by the UDP protocol, for example. The Inform message302 includes, as shown in FIG. 3B, the message type ‘Inform’ at theleading, IP address of the own medium, type of the medium, free datacapacity that can be provided for the backup, data transfer speed of theown medium, arrival time of the Inquire message, and possibility ofaccepting the backup request.

The type of the medium shows the type of the storage device, forexample, HDD (Hard Disk Drive), RAID (Redundant Arrays Of InexpensiveDisks), or magnetic tape. The free date capacity shows the latest freedata capacity of the storage device. The possibility of accepting thebackup request shows yes or no as to hiring out the storage device of acertain medium for the retention of the backup data of the other media.When there is a margin in the storage capacity of the storage device ofthe medium, it is expected that the margin is hired out to the others.

While mutually exchanging the Inquire message and the Inform messagebetween the media 101 to 105, each of the media 101 to 105 analyzes theInform message, and builds up the media information management table 400as shown in FIG. 4. This table is registered in the storage device ofeach medium.

In FIG. 4, the media information management table 400 is registered inthe storage device of a nonvolatile memory and the like, in the order ofreceiving the Inform message. That is, the information of the type ofthe media, free data capacity, data transfer speed, distance on thenetwork, and possibility of accepting the backup request are stored incorrespondence with each of the IP addresses of the media of theoriginators. Here, the distance on the network represents the distanceobtained by calculating the path until the medium as the transferdestination of data, by means of, for example, the metric used in therouting of data on the network. The processing up to here may beexecuted at each given constant intervals, by use of the timer 1103, CPU1101, and memory 1102.

Now, suppose that the media 101 detects a hardware error of its own.Here, referring to the table shown in FIG. 4, the medium 101 judges theerror condition of the own medium, and selects the most appropriatemedium to itself among the other media as a candidate for the backuprecipient. For example, the medium of which type is the RAID, the mediumof which data transfer speed is high, the medium of which free datacapacity is abundant, the medium of which distance on the network isshort, the medium on the same network address, and the media with theabove conditions combined are selected as the candidate.

Next, as shown in FIG. 1C, the medium 101 sends a Request Backup message303 to the other media selected as the backup recipient by the TCPprotocol, for example. Here, the Request Backup message 303 is composedof, as shown in FIG. 3C, the message type Request Backup at the leading,IP address of the own medium, and data transfer capacity required forthe backup.

The other media 102 to 105 having received the Request Backup messagejudge whether the backup of the requested data capacity is acceptable ornot, from the operational conditions of the own media. If the judgmentresult shows that the backup request is acceptable, the media return anAccept Backup message 304. Here, the Accept Backup message 304 includes,as shown in FIG. 3D, the message type Accept Backup, IP address of theown medium, and data transfer capacity that can be used for the backup.Here, the medium 101 to which the message 304 should be sent back can beidentified with reference to the IP address inside the received RequestBackup message 303.

On the contrary, if the judgment result shows that the backup request isnot acceptable, for example, if the free data capacity of the storagedevice is insufficient, the media return a Decline Backup message 305.Here, the Decline Backup message 305 is composed of, as shown in FIG.3E, the message type Decline Backup and IP address of the own medium.

The medium 101 receives the Accept Backup message 304 or the DeclineBackup message 305, and registers the contents of the received AcceptBackup message 304 on a backup media management table 500.

The backup media management table 500 is to register the information ofthe other media that can be an object for the backup, and as shown inFIG. 5, the table registers the information relating to the acquired IPaddress of the other media, type of the medium, data transfer capacity,and data transfer speed. Here, the information except for the datatransfer capacity is acquired from the media information managementtable 400 as shown in FIG. 4. The backup media management table 500additionally registers the total quantity of data that the own medium101 has to back up, and the acquired current total quantity of thebackup data of the other media. The backup media management table 500 isbuilt up in each of the media through the same process.

The Accept Backup message 304 is sequentially received from many othermedia. In the example of FIG. 5, the total quantity of data that the ownmedium 101 has to back up is 10000 GB, and the acquired current totalquantity of the backup data of the other media is 9800 GB, which showsthat the media is not in a position to back up yet. In contrast to this,the example of the backup media management table 500 as shown in FIG. 6shows that the media reaches a position to backup. That is, the acquiredcurrent total quantity of the backup data of the other media is 10800GB, which exceeds the data capacity of the backup object, namely, thetotal quantity of data (10000 GB) that the own media 101 has to back up.

When the total capacity of the media being the backup recipient is notyet sufficient to the quantity of the backup data, the Request Backupmessage 303 is sent again to the medium listed as the candidate for thebackup recipient, and the operation is repeated which receives theAccept Backup message 304 from the medium.

That is, the media registered in the media information management table400 excluding the media registered in the backup media management table500 in FIG. 5 are sequentially selected from the top of the managementtable 400, for example. The Request Backup message 303 is again sent tothe medium selected by the above method, and the Accept Backup message304 is received from the medium. The contents of the received AcceptBackup message 304 and the relevant information are sequentiallyregistered in the backup media management table 500 in FIG. 5. Each timewhen new media information is registered in the backup media managementtable 500, the total data capacity that can be used for the backup; andthe total data capacity thus updated is compared with the quantity ofdata being the backup object. And, when the total data capacity that canbe used for the backup exceeds the quantity of data being the backupobject, it is recognized that the data capacity necessary for the backupis ensured. When it reaches this state, the data capacity more than thisis unnecessary, and the Request Backup message 303 is not sent again.

As the total data capacity of the media that should be backed up isensured, the backup data is sent to the other media being the backupobject. This is carried out by the medium 101 sending a Deposit Backupmessage 306 for sending the backup data to the media registered in thebackup media management table 500 in FIG. 6 (see FIG. 1E). Here, theDeposit Backup message 306 is composed of, as shown in FIG. 3F, themessage type indicating the Deposit Backup, IP address of the ownmedium, physical location of data of the own medium or logical file namewith absolute path, and backup data body. In this manner, the backupdata is sequentially sent to the other media by the message 306 beingsent. The other media having received the message 306 store the receivedbackup data in the storage devices of the own media.

Now, as described above, the medium 101 receives the Accept Backupmessage 304, and the information of the media capable of backup isregistered in the backup media management table 500 in FIG. 5 (or FIG.6); then, it is possible that the free data capacity of the other mediaexceeds by far the data quantity that the medium 101 has to back up. Inthat case, the medium 101 sends the above Deposit Backup message 306 tothe currently selected media as the backup recipient; however, themedium 101 sends a Refuse Backup message 307 to the other registeredmedia than the selected ones. Thereby, the other media having receivedthe Refuse Backup message 307 can recognize it unnecessary to preparethe backup for the medium 101. Accordingly, these media can provide thecapacity ensured for the backup to the other media than the medium 101.Here, the Refuse Backup message 307 is composed of, as shown in FIG. 3G,the message type Refuse Backup and IP address of the own medium 101.

Now, as the message 306 is sent, the backup data is sequentially sent tothe other media; as the backup processing is carried out, a detail(hereunder, mentioned as manifest) table 700 for the log control iscreated in the medium 101 being the source, which is archived in thenonvolatile memory 1104. A deposit table 800 is created in the othermedia having received the backup data, which is archived in thenonvolatile memory 1104. These tables 700, 800 may be archived in therecording medium 1105.

Referring to FIG. 7, the manifest table 700 registers the information ofbackup data map, transfer start time, transfer termination time, andsuccess/failure flag in correspondence with the IP address of the mediumbeing the transfer destination of the backup data. Here, the backup datamap includes the information of logical volume number as the addresswhere the backup data is stored, cylinder number, and track number. Thisexample shows that the backup data is transferred to two media ofdifferent IP addresses.

The manifest table 700 is retained in the nonvolatile memory 1104 of theown medium 101, and additionally, the table may be transferred to theother media 102 to 105 that transferred the backup data, as shown inFIG. 1F, and may be stored in the nonvolatile memory 1104 of the mediumbeing the transfer destination; thus, both media may retain the table.

FIG. 8 illustrates a configuration of a deposit table 800 in the mediumthat accepted the backup. The deposit table 800 registers theinformation of backup data map, receive start time, receive terminationtime, and success/failure flag in correspondence with the IP address ofthe medium being the sending originator of the backup data. The exampleof FIG. 8 finds that the media having this deposit table 800 accepts thebackup from two medium having different IP addresses.

Next, the method of restoring the data having been backed up will bedescribed with reference to FIG. 2. As a premise, there occurs anabnormality in the medium 101, and the data of the media 101 are backedup in the media 102 to 105. The nonvolatile memory 1104 of the medium101 retains the manifest table 700 for managing the backup data.

Now, the abnormality in the medium 101 is mended, and the restoration ofthe backup data will be made to the medium 101. The restoration modestarts with the input of restoration instruction by the system manager.When the medium 101 has a small capacity medium, the medium 101 may beput in the restoration mode when the small capacity medium is set.

First, as shown in FIG. 2A, the CPU 1101 of the medium 101 analyzes thecontents of the manifest table 700. As a result of the analysis, tostart the restoration, the medium 101 sends a Request Restore message901 by means of the unicast, for example, to the other media having theIP address in the table 700 (see FIG. 2B). The Request Restore message901 includes the message type Request Restore and IP address of the ownmedium 101, as shown in FIG. 9A.

The other media that received the Request Restore message return anAccept Restore message 902 if it is possible to transfer the restorationinformation immediately; and if it is impossible to transfer therestoration information immediately, the other media return a LateRestore message 903, as shown in FIG. 2C. The address of the mediumbeing the return destination can be identified with reference to the IPaddress contained in the Request Restore message. The Accept Restoremessage 902 includes the message type Accept Restore and IP address ofthe own medium 101, as shown in FIG. 9B. The Late Restore message 903includes the message type Late Restore and IP address of the own medium101, as shown in FIG. 9C.

Receiving the Accept Restore message 902 or the Late Restore message903, the medium 101 creates a restoration management table 1000 (seeFIG. 10), and retains it in the nonvolatile memory 1104. The restorationmanagement table 1000 is the management table for acquiring andrestoring the backup data, which registers the information of IP addressof the media being the recipient of the backup data, backup data map,transfer start time, transfer termination time, and restorability flag.The IP addresses are the same as the one registered in the manifesttable 700.

The backup data map shows the location where the backup data to beacquired is restored. This backup data map shows the physical locationof data on the media in this example, however it may show the logicallocation with an absolute path. The restorability flag Y (possible) isgiven to the media that returned the Accept Restore message 902, and theflag N (impossible) is given to the media that returned the Late Restoremessage 903. In the example of FIG. 10, the restoration of the date fromthe media of the IP address ‘192.168.0.3’ is completed, and therestoration of the date from the media of the IP address ‘192.168.0.4’is now being executed.

Next, the medium 101 waits for a Withdraw Restore message 904 being sentfrom the media that returned the Accept Restore message 902. TheWithdraw Restore message 904 includes, as shown in FIG. 9D, the messagetype Withdraw Restore, IP address of the own medium, physical locationof data of the own medium or logical file name with an absolute path,and backup data body.

Receiving the Withdraw Restore message 904, the medium 101 writes thestart time of restoring the backup data, and the termination time of therestoration into the restoration management table 1000. To the mediathat returned the Late Restore message 903, the medium 101 sends theRequest Restore message 901 at each constant time intervals by means ofthe unicast, for example.

In this manner, when the backup data is restored by the data from themedia corresponding to the IP address in the restoration managementtable 1000, the start time and termination time of the table are allfilled, and all the restorability flags become Y, the data restorationin the medium 101 is all completed. On the other hand, the other media102 to 105 that completed transferring the backup data to the medium 101delete the data being backed up from the recording medium 1105. Althoughnot especially explained, the above embodiment may utilize the generallyused encryption algorithm to encipher the backup data before thetransfer of the backup data.

The above embodiment described that the memory to archive the manifesttable 700 was the nonvolatile memory 1104. However, a medium such as amemory card may be used as the recording medium dedicated for themanifest table, instead of the nonvolatile memory 1104. In this case,the memory card should be detachable to the port to which the memorycard is connected.

Further, it may be configured that, until the data restoration of themedium is completed, the contents of the memory cord of the own mediumare set un-rewritable, and when the restoration is completed, thecontents of the manifest table of the memory card are set rewritableagain, thus automatically acquiring the backup management informationwith the preparation for an abnormality that can occur again in thefuture.

Further, it may be configured to create a restoration log based on therestoration management table 1000 in FIG. 10, and write it in asmall-capacity medium that the own medium contains. By thisconfiguration, when a certain medium detects an abnormal state byitself, the other media connected to the network accommodate free areasmutually automatically without intervention of operators, and the mediumis able to back up the data inside the medium being in the normal state.

1. A method of backing up data stored on a first information processingunit, using plural second information processing units connected to anetwork, comprising the steps of: sending autonomously a first messagefrom the first information processing unit to the plural secondinformation processing units, the first message inquiring as to apossibility of backing up the data stored on the first informationprocessing unit to the plural second information processing units;receiving second messages at the first information processing unit fromsaid plural second information processing units that responded to thefirst message, said second messages containing information as to thepossibility of backing up the data stored on the first informationprocessing unit; creating a first table on the basis of the secondmessage by the first information processing unit, the first tablemanaging at least information relating to the plural second informationprocessing units capable of backing up the data, and retaining the firsttable at the first information processing unit; distributing the datastored on the first information processing unit as backup data toselected second information processing units as recipients of the backupdata, said selected second information processing units being selectedby the first information processing unit from the first table bycomparing an amount of data each of said second information processingunits is capable of backing up to a total amount of the data on thefirst information processing unit to be backed up, and by sendingportions of the backup data to the selected second informationprocessing units based upon the amount of data each selected secondinformation processing unit is capable of backing up; creating a secondtable for managing information including an address of each of theselected second information processing units which is selected by thefirst information processing unit as a recipient of the backup data, andretaining the second table at the first information processing unit;sending a third message by the first information processing unitreferring to the second table, said third message requesting restorationof the backup data to the first information processing unit byrequesting transfer of the backup data portions from the selected secondinformation processing units, each of which was the recipient of thebackup data portions; receiving, by the first information processingunit, the backup data portions sent from the selected second informationprocessing units; and storing the received backup data portionsaccording to mapping information retained in the first informationprocessing unit to restore the data stored at the first informationprocessing unit.
 2. The method of backing up data according to claim 1,wherein the second message includes a type of a medium that the secondinformation processing unit possesses, a free capacity of the medium,and information as to whether a backup request can be accepted, and thefirst table registers an address that specifies each of the pluralsecond information processing units that received the first message, thetype of the medium, the free capacity of the medium, and the informationas to whether the backup request can be accepted.
 3. The method ofbacking up data according to claim 1, wherein the second table registersat least the address of each of the selected second informationprocessing units to which the backup data portions were sent, andinformation indicating success or failure of the backup.
 4. The methodof backing up data according to claim 1, wherein each of the selectedsecond information processing units that received one of said backupdata portions from the first information processing unit creates andstores a third table that registers at least an address of the firstinformation processing unit having been a sender of the backup dataportion, and information indicating success or failure of the backup. 5.The method of backing up data according to claim 1, wherein, beforesending the backup data portions to the selected second informationprocessing units from the first information processing unit, the methodincludes the steps of: selecting the plural second informationprocessing units as a backup object with reference to the first table,and sending a backup request message to the selected plural secondinformation processing units, said backup request message specifying adata capacity for the backup; and receiving a return message as towhether the backup request of the specified data capacity can beaccepted or not from the selected plural second information processingunits.
 6. The method of backing up data according to claim 1, furtherincluding a step of when a total amount of data on the first informationprocessing unit to be backed up exceeds a total amount of capacityavailable for backup on the plural second information processing unitsthat responded to the first message, the first information processingunit repeats the first message to one or more additional secondinformation processing units of the plural second information processingunits.
 7. The method of backing up data according to claim 1, furthercomprising a step of when a particular one of the selected secondinformation processing units is unable to transfer its particular backupportion, the particular second information processing unit sends aresponse that restoring of the particular backup portion will be late.8. The method of backing up data according to claim 7, wherein the firstinformation processing unit periodically repeats the third message tothe particular second information processing unit that sent the responsethat restoring of the particular backup portion will be late until theparticular backup portion is restored.
 9. The method of backing up dataaccording to claim 1, further including a program stored on a computerreadable medium said program causing the execution of the steps of themethod according to claim
 1. 10. A method of backing up data in a systemincluding plural information processing units connected to a network,each of said information processing units autonomously sending andreceiving data to and from multiple others of the information processingunits for enabling backing up of data stored on each informationprocessing unit to the multiple others of the information processingunits connected to the network, the steps carried out by each particularinformation processing unit when backing up the data stored thereincomprising: collecting information by the particular informationprocessing unit from the multiple other information processing unitsconnected to the network as to a possibility of backing up data fromthat information processing unit to the multiple other informationprocessing units; adding addresses for identifying each of the multipleother information processing units from which the information iscollected, and storing the collected information at the particularinformation processing unit; sending, by the particular informationprocessing unit, a backup request to selected multiple other informationprocessing units, selected by the particular information processing uniton the basis of the collected information by comparing an amount of datathat each of said selected multiple other information processing unitsis capable of backing up to a total amount of the data on the particularinformation processing unit to be backed up; and sending portions of thedata on the particular information processing unit to the selectedmultiple other information processing units as backup data portions. 11.The method according to claim 10, further comprising steps of restoringthe data on the particular information processing unit by the particularinformation processing unit sending a request to the selected multipleother information processing units requesting transfer of the backupdata portions from the selected multiple other information processingunits that were the recipients of the backup data portions; receiving,by the particular information processing unit, the backup data portionssent from the selected multiple other information processing units; andstoring the received backup data portions according to mappinginformation retained at the particular information processing unit torestore the data of the particular information processing unit.
 12. Themethod according to claim 10, further comprising a step of retaining thecollected information in a non-volatile memory of the particularinformation processing unit, wherein the collected information includesthe addresses for identifying the multiple other information processingunits and a media type of the multiple other information processingunits.
 13. The method according to claim 10, further including a step ofselecting said selected multiple other information processing units atleast partially on a basis of having a same media type as the particularinformation processing unit.
 14. The method according to claim 10,further including a step of when a total amount of data on the firstinformation processing unit to be backed up exceeds a total amount ofcapacity available for backup on the multiple other informationprocessing units that responded to the first message, the particularinformation processing unit repeats the first message to one or moreadditional other information processing units of the plural informationprocessing units.
 15. The method according to claim 10, furtherincluding a step of autonomously creating a table by each of the pluralinformation processing units in the system, the table being created fromthe collected information collected by each particular informationprocessing unit and including a type of a medium that each of the otherinformation processing units possess, a free capacity of the medium, andinformation as to whether a backup request can be accepted by the otherinformation processing units, and determining a size of the backup dataportions sent to the selected other information processing units basedupon the amount of data each selected other information processing unitis capable of backing up.
 16. A system comprising plural informationprocessing units connected to a network, each of said informationprocessing unit being capable of autonomously sending and receiving datato and from multiple others of the plural information processing unitsfor backing up data stored on each of the information processing units,each of said information processing units comprising: a CPU thatexecutes data processing; a recording medium that stores data processedby the CPU; and a communication port connected to the network and pathsto connect the information processing units, wherein the communicationport sends a first message for acquiring state information of the otherplural information processing units connected to the network, andreceives second messages sent from the other plural informationprocessing units, said second messages including information as to apossibility of backing up the data of the information processing unit tothe other plural information processing units, wherein the memory or therecording medium retains a first table, created on the basis of thesecond messages, that manages information relating to the other pluralinformation processing units being at least capable of backing up thedata of the information processing unit; wherein, when an abnormal statein the information processing unit is detected, the CPU autonomouslyselects others of the plural information processing units to be therecipients of backup data from the information processing unit byreferring to the first table and comparing an amount of data each of theother plural information processing units is capable of backing up to atotal amount of the data on the information processing unit to be backedup, issues a backup request to the selected other information processingunits, and executes processing for sending portions of the data storedin the recording medium as backup data portions to the selected otherinformation processing units that accepted the backup request.
 17. Thesystem according to claim 16, wherein, to restore the data of theinformation processing unit, the CPU requests transfer of the backupdata portions from the selected other information processing units thatbecame the recipients of the backup data portions; the communicationport receives the backup data portions sent from the selected otherinformation processing units; and the recording medium stores thereceived backup data portions, whereby the data of the informationprocessing unit is restored, wherein the memory or the recording mediumstores a restoration management table for correctly restoring thereceived portions of the data according to mapping information.
 18. Thesystem according to claim 16, wherein each of the plural informationprocessing units in the system autonomously creates one of said firsttables, each said first table containing state information of the otherinformation processing units in the system, the first table beingcreated from collected second messages received by each particularinformation processing unit in response to said first messages sent bythat particular information processing unit, said first table includinga type of a medium that each of the other information processing unitspossess, a free capacity of the medium, and information as to whether abackup request can be accepted by the other information processingunits.
 19. The system according to claim 16, wherein, when a totalamount of data on the information processing unit to be backed upexceeds a total amount of capacity available for backup on the otherplural information processing units that responded to the first message,the information processing unit repeats the first message to one or moreadditional other information processing units of said plural informationprocessing units.
 20. The system according to claim 16, wherein a sizeof the backup data portions sent to the selected other informationprocessing units is based at least in part on the amount of data each ofthe selected other information processing units is capable of backingup.